broken-neees/cpu/addressingModes.js

A really broken NEEES emulator that introduces glitches and random bugs on purpose!

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _byte = _interopRequireDefault(require("../lib/byte"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
const unsupported = () => {
  throw new Error("Unsupported.");
};
function read(cpu, argument, hasPageCrossPenalty) {
  return cpu.memory.read(this.getAddress(cpu, argument, hasPageCrossPenalty));
}
const addressingModes = {
  IMPLICIT: {
    inputSize: 0,
    getAddress: () => null,
    getValue: unsupported
  },
  IMMEDIATE: {
    inputSize: 1,
    getAddress: unsupported,
    getValue: (cpu, value) => value
  },
  ABSOLUTE: {
    inputSize: 2,
    getAddress: (cpu, address) => address,
    getValue: read
  },
  ZERO_PAGE: {
    inputSize: 1,
    getAddress: (cpu, zeroPageAddress) => zeroPageAddress,
    getValue: read
  },
  RELATIVE: {
    inputSize: 1,
    getAddress: (cpu, offset, hasPageCrossPenalty) => {
      const address = cpu.pc.getValue();
      const newAddress = address + _byte.default.toS8(offset);
      const pageCrossed = _byte.default.highByteOf(address) !== _byte.default.highByteOf(newAddress);
      if (pageCrossed && hasPageCrossPenalty) cpu.extraCycles += 2;
      return _byte.default.toU16(newAddress);
    },
    getValue: unsupported
  },
  INDIRECT: {
    inputSize: 2,
    getAddress: (cpu, absoluteAddress) => {
      const msb = _byte.default.highByteOf(absoluteAddress);
      const lsb = _byte.default.lowByteOf(absoluteAddress);
      const low = cpu.memory.read(absoluteAddress);
      const high = cpu.memory.read(lsb === 0xff ? _byte.default.buildU16(msb, 0x00) : absoluteAddress + 1);
      return _byte.default.buildU16(high, low);
    },
    getValue: unsupported
  },
  INDEXED_ZERO_PAGE_X: {
    inputSize: 1,
    getAddress: (cpu, zeroPageAddress) => {
      return _byte.default.toU8(zeroPageAddress + cpu.x.getValue());
    },
    getValue: read
  },
  INDEXED_ZERO_PAGE_Y: {
    inputSize: 1,
    getAddress: (cpu, zeroPageAddress) => {
      return _byte.default.toU8(zeroPageAddress + cpu.y.getValue());
    },
    getValue: read
  },
  INDEXED_ABSOLUTE_X: {
    inputSize: 2,
    getAddress: (cpu, absoluteAddress, hasPageCrossPenalty) => {
      const address = absoluteAddress;
      const newAddress = address + cpu.x.getValue();
      const pageCrossed = _byte.default.highByteOf(address) !== _byte.default.highByteOf(newAddress);
      if (pageCrossed && hasPageCrossPenalty) cpu.extraCycles += 1;
      return _byte.default.toU16(newAddress);
    },
    getValue: read
  },
  INDEXED_ABSOLUTE_Y: {
    inputSize: 2,
    getAddress: (cpu, absoluteAddress, hasPageCrossPenalty) => {
      const address = absoluteAddress;
      const newAddress = address + cpu.y.getValue();
      const pageCrossed = _byte.default.highByteOf(address) !== _byte.default.highByteOf(newAddress);
      if (pageCrossed && hasPageCrossPenalty) cpu.extraCycles += 1;
      return _byte.default.toU16(newAddress);
    },
    getValue: read
  },
  INDEXED_INDIRECT: {
    inputSize: 1,
    getAddress: (cpu, zeroPageAddress) => {
      const start = _byte.default.toU8(zeroPageAddress + cpu.x.getValue());
      const end = _byte.default.toU8(start + 1);
      return _byte.default.buildU16(cpu.memory.read(end), cpu.memory.read(start));
    },
    getValue: read
  },
  INDIRECT_INDEXED: {
    inputSize: 1,
    getAddress: (cpu, zeroPageAddress, hasPageCrossPenalty) => {
      const start = _byte.default.toU8(zeroPageAddress);
      const end = _byte.default.toU8(start + 1);
      const address = _byte.default.buildU16(cpu.memory.read(end), cpu.memory.read(start));
      const newAddress = address + cpu.y.getValue();
      const pageCrossed = _byte.default.highByteOf(address) !== _byte.default.highByteOf(newAddress);
      if (pageCrossed && hasPageCrossPenalty) cpu.extraCycles += 1;
      return _byte.default.toU16(newAddress);
    },
    getValue: read
  }
};
for (let key in addressingModes) {
  addressingModes[key].id = key;
}
var _default = exports.default = addressingModes;